Neospora caninum is a protozoan parasite. It was isolated from brain of naturally infected rats and fed on puppies. Five to ten days post-infection, puppies began to excrete unsporulated oocysts. Sporulat­ed oocycts were fed to rats. After death, fresh smears from intestines of puppies and brain smears stained with Giemsa stain from rats were taken for parasitological examination. Meanwhile, tissue specimens from the internal organs wer taken from puppies and rats for histopathological examination. However, only brains from rats were taken for electron mi­croscopy examination. Histopathological examination revealed meningoencephalomyeli­tis, hepatitis, nephrosis and occasional interstitial pneumonia in puppies and rats, in addition to myocarditis and myocitis in puppies. Tissue cysts and tachyzoites were present in lesions in the brain of rats. In puppies, tachyzoites were seen in the brain and in parasitophorous vacuoles with­in the cytoplasm of epithelium lining the small intestine. Electron microscopy examination of the brain of rats revealed ta­chyzoites and tissue cysts. Parasitological and pathological importance of N. caninum in pup­pies and rats was fully discussed.